Infinitive "Haljeta" after olla. What's is this structure?

This is an excerpt from an interview. The full phrase is "Äidit ja isät olivat haljeta ylpeydestä."

I know it should be saying "Our mother's and father's were bursting with pride", but I don't get why the word "haljeta" comes after olivat. How can you just put a verb after olla like that? As far as I know in Finnish grammar there is no grammatical structure where a verb infinitive is simply put after a conjugation of olla. What's the difference if one just said "Äidit ja Isät halkesivat"? Is there a change in meaning?